Re: [PATCH] [GSOC] ref-filter: solve bugs caused by enumeration

From: Junio C Hamano <gitster@pobox.com>
To: ZheNing Hu <adlternative@gmail.com>
Cc: ZheNing Hu via GitGitGadget <gitgitgadget@gmail.com>,
	Git List <git@vger.kernel.org>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH] [GSOC] ref-filter: solve bugs caused by enumeration
Date: Fri, 07 May 2021 13:49:47 +0900	[thread overview]
Message-ID: <xmqq5yzvw3kk.fsf@gitster.g> (raw)
In-Reply-To: <CAOLTT8QWadP9ovrUC_7m86dKh1PsawUyZ=msK5tx1utTpuCXMQ@mail.gmail.com> (ZheNing Hu's message of "Fri, 7 May 2021 12:32:25 +0800")

ZheNing Hu <adlternative@gmail.com> writes:

> But I am afraid that the cost we paid for string matching here is too high,

If that is truly the concern (I do not know without measuring),
perhaps we should add a member next to the union to say which one of
the union members is valid, so that you can say

    if (atom->atom_type == ATOM_TYPE_REMOTE_REF &&
        atom->u.remote_ref.push)

(introduce an enum and define ATOM_TYPE_* after the member in the
union).

That would help futureproofing the code even further, as a new
synonym of "push" introduced laster [*] would not invalidate the check you are
adding there.

[Footnote]

* remote_ref_atom_parser() in the future may begin like so:

-	if (!strcmp(atom->name, "push") || starts_with(atom->name, "push:"))
+	if (!strcmp(atom->name, "push") || starts_with(atom->name, "push:") ||
+           !strcmp(atom->name, "a-synonym-for-push"))
		atom->u.remote_ref.push = 1;